1. Field of the Invention
The present invention relates to a buffer and organic light emitting display and a data driving circuit using the buffer, particularly to a buffer and organic light emitting display and a data driving circuit using the buffer that are able to provide an accurate output voltage regardless of the threshold voltage of a transistor.
2. Discussion of Related Technology
Various flat-panel displays have been developed so as to have less weight and bulk than that of a CRT (Cathode Ray Tube). Flat-panel displays include liquid crystal displays, electric field emission displays, plasma display panels, and organic light emitting displays, as well as others. An organic light emitting display presents an image using organic light emitting diodes that emit light from the recombination of electrons and holes. The organic light emitting display creates a data signal using input data from an outside source and displays an image having a desired brightness by supplying the generated data signal to pixels using at least a data driving circuit and data lines.
The data driving circuit converts the input data into a voltage corresponding to a gray scale value and supplies the converted voltage to data lines as a data signal via a buffer. Each respective pixel receives an electrical current corresponding to the voltage from the driving circuit. As a result, the organic light emitting diode within each pixel emits light according to the current it receives and a predetermined image is displayed.
In the above mentioned data driving circuit, the buffer should supply the data signal to a pixel without a voltage drop between its input and output. However, conventional buffers supply a data signal with a voltage drop corresponding to a threshold voltage of a transistor. Because of this, the voltage of the data signal is dropped by as much as a transistor threshold voltage and the result is that pixels are not able to display the image with a desired brightness.